In modern motor vehicles, soft chassis springs are used for a high driving comfort. In combination with correspondingly designed shock absorbers, such an improved ground contact is guaranteed in case of road unevennesses. The unfavorable increase in the rolling angle in curves which occurs in this case is compensated by the use of stabilizers, whereby the stabilizers are attached to the vehicle chassis and are connected in an articulated manner at the ends to a spring-mounted wheel carrier part, e.g., a suspension arm or a rigid axle via a rocker pendulum each. However, the possible axle twisting is reduced by the use of stabilizers, since they restrict an inward deflection in the opposite direction of the wheels of an axle. Therefore, it is especially desirable for off-road vehicles, so-called SUVs, to make it possible to influence the stabilizer function during off-road driving. This can be guaranteed by the use of switchable components, such that the wheels of an axle can deflect from one another independently. In this way, all wheels of the vehicle hold contact with the ground and can transmit propulsive forces.
There is a possibility of using switchable components in the use of hydraulically length-variable adjusting elements, such as, e.g., piston-cylinder units, instead of fixed rocker pendulums, as this is disclosed, e.g., in U.S. Pat. No. 4,206,935. The length-variable piston-cylinder units arranged between the stabilizer and the motor vehicle chassis are connected to one another by hydraulic lines, whereby the cylinder chamber facing towards the stabilizer and the cylinder chamber facing away from the stabilizer are each connected to one another via a hydraulic line each. A valve, which can block or release both hydraulic lines at the same time, is inserted into these hydraulic lines. If the hydraulic lines are blocked, the pistons of the piston-cylinder units are blocked, so that the stabilizer is able to transmit rolling motions of the vehicle to the other side of the vehicle. By contrast, if the hydraulic line is released, the pistons are able to move freely in the cylinders in case of rolling motions of the vehicle, such that the rolling motions cannot be absorbed by the stabilizer. In this case, hydraulic fluid flows from one piston-cylinder unit into the other.
The drawback of this arrangement is that, when the hydraulic lines are blocked, the pistons are not located in a defined and determinable position in the cylinders. Therefore, the stabilizer may be located outside of the structural position or fitting position, such that the driving properties are affected negatively.
Another arrangement for switchable rocker pendulums is used in the off-road vehicle Nissan Patrol. A coupling, consisting of a spring-loaded bolt on a piston, whereby the bolt meshes with a hole of the piston and thus blocks the piston, acts in this system of a piston-cylinder unit. If the coupling is released, the piston can move freely in the cylinder. The drawback of this embodiment is that the bolt only meshes with the hole when the bolt and hole are aligned with one another. The user has no effect on this. In the worst case, the vehicle travels without any stabilizer action in spite of the coupling being actuated. The driver does not receive any feedback in this system as to whether the piston is blocked.